Trimethoprim-Sulfamethoxazole Effective Regardless of Abscess Size

Trimethoprim-sulfamethoxazole treatment was associated with improved outcomes in patients with drained skin abscesses regardless of lesion size or guideline criteria, according to a study published in the Annals of Emergency Medicine.

Two large trials in the United States recently showed that patients with skin abscesses receiving primary treatment (drainage) had improved outcomes when also treated with trimethoprim-sulfamethoxazole (ClinicalTrials.gov identifier: NCT00729937). The follow-up analysis tested whether these improved outcomes persisted among subgroups with and without conditions for which antibiotics have been selectively recommended.

The subgroups selected for analysis were patients with abscess cavity or erythema maximal dimension ≥5 cm; those with history of methicillin-resistant Staphylococcus aureus (MRSA) infection; patients with fever, diabetes, or major comorbidities such as eczema or chronic edema, chronic obstructive pulmonary disease, congestive heart failure, HIV infection, or cancer; and patients with positive culture for MRSA or methicillin-susceptible S aureus. The primary outcomes were the difference in abscess clinical cure rates, defined here as the resolution of all symptoms and signs of infection, or improvement so that no additional antibiotic medications were prescribed any time 7 to 14 days after treatment ended.

Overall 92.9% of patients receiving trimethoprim-sulfamethoxazole achieved the primary outcome, whereas this occurred in only 85.7% of the placebo group, a difference of 7.2 (95% CI, 3.2-11.2). Cure rates remained higher for the treatment group compared with the placebo group in each of the clinical subgroups.

The improved outcomes were seen regardless of abscess or erythema dimensions, but the greatest cure effect was seen in subgroups identified by guidelines for antibiotic treatment, such as those with history of MRSA infection and fever. Further study could validate these findings and lead to improved decision making between clinicians and patients regarding treatment options and costs.